(a) Field Of The Invention
Prior Art
In conjunction with flywheel magneto systems there is always a problem of being able to achieve as large a number of operation and control functions as possible while using a minimum number of components in the relatively small space available. Accordingly, from the design and construction aspect it is suitable to concentrate voltage generating windings on one core and in one magnetic path (one circuit). From the aspect of winding technique it is further advantageous if several coils can be wound in the same winding direction. The patent literature contains many solutions to the problem mentioned above. The ignition systems customarily used in such connections are so-called capacitive ignition systems, i.e. systems in which the potential energy stored in a capacitor is utilized for providing an ignition spark. The prevailing construction of such ignition systems includes the arrangement of a charging winding in the existing flywheel magneto, this winding generating charging voltage to a capacitor via a rectifier. The capacitor is connected to the primary circuit in an ignition transformer and forms, together with a thyristor, a series circuit for a subsequent discharge of the charged state in the capacitor. The thyristor gets its control voltage from a trigger winding in the system, which generates voltage pulses for triggering the thyristor.
The simplest solution for inhibiting an ignition sequence in a circuit according to the prior art is to shortcircuit or bypass the charge capacitor. This is not suitable in practice however, since there may be potentials of up to 400 volts and more across the charge capacitor. For the sake of safety, such voltage levels should not be lead out to stop button functions for manual operations. The next solution nearest available is to keep a thyristor in a system in a non-conductive state in some way, to prevent the capacitor discharge. In this connection there occurs the problem that for smoothing out over-voltages occurring during retarding the engine and for this purpose a varistor or the like must be arranged across the charging rectifier.